The present invention relates to an operational amplifier, and more particularly to stages of an operational amplifier including a class AB source follower output stage.
A conventional mixed mode integrated circuit system frequently uses different voltage supplies. Typically some analog signal processing, such as amplification, comparison, pulse generation, is performed at high voltage. A conventional operational amplifier that operates at high voltage (e.g., 14V) requires transistors and other devices that meet high voltage break down requirements, such as breakdown voltage of the drain with gate and source shorted to ground (BVDSS), breakdown voltage of the drain with gate shorted to ground and source floating (BVDSF), and breakdown voltage of gate oxide layer (BVOX). Conventional operational amplifiers use transistors with breakdown voltages that can sustain a HV supply.